The present invention relates to a spring chuck built in a head case at a front end portion of a handpiece used as a medical or dental cutting or polishing tool, a jewel cutting or polishing tool or an industrial cutting or polishing tool.
In a conventional handpiece, a head case houses a hollow rotating shaft, a bar stopper rotatably mounted inside the rear end portion of the rotating shaft, a bar checker fixed inside the front end portion of the rotating shaft, and a coil spring clamp member one end of which is fixed to the bar stopper and the other end of which is fixed to the bar checker.
A clamp member of this type is opened when one of the rotating shaft and the bar stopper is fixed and the other thereof is rotated against the torsional force of the clamp member so as to apply force on both ends of the clamp member. When the force acting on one of the rotating shaft and the bar stopper is removed, the clamp member is closed by its torsional force. When the clamp member is opened by a clamp member opening means, this clamp member opening means must have a member for fixing one of the rotating shaft and the bar stopper to the head case, and a member for rotating the other thereof in a direction opposite to the winding direction of the clamp member. However, according to the method in which only one of the rotating shaft and the bar stopper is rotated, the rotational angle of the rotating shaft or the bar stopper is increased, and a drive mechanism for the rotating shaft or the bar stopper becomes large in size. The clamp member opening means cannot be housed inside the head case. For this reason, the handpiece is separated from the clamp member opening means, and the opening operation of the clamp member becomes complicated when a cutting tool or the like is mounted in or detached from the handpiece, resulting in inconvenience.